Wheel bearings allow wheels to rotate freely and accurately hold the brake discs or drums. Most common wheel bearings are tapered roller bearings or ball bearings, which are lubricated with grease. Hub and wheel bearings are used on non-driving and driving wheels. On non-driving wheels, the spindle is stationary and the hub is greased to lubricate the bearings. On driving wheels, the axle shaft rotates inside a stationary support and the hub is splined to the axle shaft. Four-wheel drive systems use a locking hub mechanism to transfer power between the front axle and hub. Lack of lubrication in wheel bearings can cause noise, roughness, or looseness due to

1. WHEEL BEARING
DESIGN, DIAGNOSIS,
& REPAIR

2. Allow the wheel to turn freely around the spindle, in the
steering knuckle, or in the bearing support
Most wheel bearings are tapered roller bearings or ball
bearing
Accurately hold disc or drum in true to minimize brake
pulsation

3. TAPERED ROLLER BEARING
Lubricated with high-temperature grease

4. BALL BEARING
Balls allow parts to rotate with a minimum amount
of friction and wear

5. HUB AND WHEEL BEARING
(NON-DRIVING WHEELS)
Spindle is stationary, providing a mounting place for
the wheel bearings, hub, and wheel
Hub is partially filled with grease to lubricate the
bearings
Nut on the end of the spindle allows adjustment of
the bearing preload

6. HUB AND WHEEL BEARING
(NON-DRIVING WHEELS)

7. HUB AND WHEEL BEARING
(NON-DRIVING WHEELS)
Used on the front of rear-wheel-drive cars or the
rear of front-wheel-drive cars

8. HUB AND WHEEL BEARING
(DRIVING WHEELS)
Axle shaft rotates inside a stationary support
Drive shaft fits through the center of the bearings
Hub is splined to the axle shaft
Ball bearings are lubricated by thick, high-
temperature grease

9. HUB AND WHEEL BEARING
(DRIVING WHEELS)

10. HUB AND WHEEL BEARING
(DRIVING WHEELS)
Commonly used on the front of front-wheel-drive
vehicles

11. HUB AND WHEEL BEARING
(FOUR-WHEEL DRIVE)
Front drive axle extends through a stationary spindle
Special free-wheel, or locking hub transfers power
from the axle to the hub-disc assembly when in four-
wheel-drive

12. HUB AND WHEEL BEARING
(FOUR-WHEEL DRIVE)
Front axle, brakes, hub, and wheel bearing
assembly

13. WHEEL BEARING NOISE
Produced by a dry, worn wheel bearing
When balls or rollers are damaged from lack of
lubrication, they may emit a humming or growling
sound
Checking the bearings:
 raise the vehicle on a lift
 rotate the tire by hand
 feel and listen for bearing roughness
 wiggle the tire to check for looseness

14. Wheel bearings are normally filled with grease
If the grease dries out, the bearing will fail
Some bearings are serviceable
Some bearings are sealed units

15. Questions? Questions?
Bueller…